Numerical Model for Minimizing Risk of Damage in Repair System

Martinola, Giovanni; Sadouki, H.; Wittmann, Folker H.

doi:10.1061/(asce)0899-1561(2001)13:2(121)

Cited by 17 publications

(6 citation statements)

References 5 publications

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“…Fracture energy of the interface is considered as a main parameter representing the interface fracture behaviour by many researchers (Kunieda et al 2000;Martinola et al 2001;Lau and Büyüköztürk 2010). Cement based materials exhibit a non-linear stress-strain relationship and microcracking before the peak stress.…”

Section: Simulation Results and Discussionmentioning

confidence: 99%

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Luković

Šavija

Dong

et al. 2014

ACT

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Micromechanical interface properties in a concrete repair system determine the performance and reliability of a repaired structure. In order to characterize these properties, nanoindentation technique was applied. Three different repair material mixtures, based on Portland cement or partial replacement of Portland cement with blast furnace slag, were tested. Hardness and elastic modulus values obtained from the nanoindentation were used directly as input for simulated direct tension test. This way, the fracture behaviour of original microstructure, "mimicked" by Delft lattice model, is analysed. Backscattered electron (BSE) image analysis is utilized to estimate the average size of the interface zone which is distinguished as locally more porous area. This, together with simulation results, is further used for calculation of the interface stiffness. Simulation results enable prediction and better insight into fracture propagation and micromechanical response of the tested zone. They also indicate the ratio between interface and bulk material fracture properties when different types of repair materials are used. Load displacement diagrams of interface, old and new material can serve as an input for numerical modelling and understanding of fracture behaviour of the repair systems at the higher scale. Potentially, this approach may develop as a tool for verifying and engineering interface properties such that desired performance of the repaired structure is achieved.

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Section: Simulation Results and Discussionmentioning

confidence: 99%

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Luković

Šavija

Dong

et al. 2014

ACT

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“…For coupling moisture and fracture analysis, it can be assumed that the moisture distribution produces a shrinkage field according to equation [3]:

ε_{s h} = α_{s h} ∆ H

where ε sh is the unrestrained shrinkage strain, Δ H is the change in relative humidity and α sh hygral coefficient of shrinkage which can be measured from drying tests at different relative humidities. Hygral coefficients were taken from experimental measurements of Martinola and Wittmann [12]: for repair material α sh,RM = 0.0048; for interface between repair material and substrate α sh,INT = 0.0028; and for substrate α sh,SUB = 0.0013.…”

Section: Modelling Approachmentioning

confidence: 99%

“…Also, a number of two-dimensional continuum models were used [3,9,10,11,12,13]. One way of coupling moisture transport and fracture simulations, while taking into account the influence of drying on cracking mechanism, is through discrete lattice type modelling [14,15].…”

Section: Introductionmentioning

confidence: 99%

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A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

Luković¹,

Šavija²,

Schlangen³

et al. 2016

Materials

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Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined.

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“…The thermal analysis is a conventional heat transfer analysis involving conduction and convection heat transfer modes and body heat flux to simulate the exothermic hydration process. The hygral analysis is performed in a similar way using the analogy between heat and hygral flux and using the concept of diffusivity with unit values of densities and specific heat [17]. In both cases, the simulation period of time can be as large as the lifetime span tlife of the structure.…”

Section: Multi-physical Approachmentioning

confidence: 99%

Development of a computational multi-physical framework for the use of nonlinear explicit approach in the assessment of concrete structures affected by alkali-aggregate reaction

Ftima

Sadouki

Brühwiler

2016

Proceedings of the 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures

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This paper proposes an innovative methodology for the use of the explicit approach in the assessment of concrete structures affected by alkali-aggregate reaction (AAR). Efficiency of the explicit approach has been proven in previous works for the case of large concrete structural models with high degree of nonlinearity. In the proposed methodology, the strain is decomposed into mechanical, thermal, creep, shrinkage and AAR strain components. The AAR component is computed according to Saouma and Perotti model [1] for the anisotropic distribution of the volumetric expansion and according to Larive model [2] for the AAR kinetics. One advantage of the approach is that it can be used with any existing concrete model that has undergone a rigorous verification and validation (V&V) process for the mechanical part. In this work the EPM3D concrete model [2] implemented as a user-subroutine in Abaqus-Explicit is used. The general methodology is based on three different finite element analyses: thermal implicit, hygral implicit and the final nonlinear multiphysical explicit analysis. An innovative formulation to address the problem of time scale difference between the implicit and explicit approaches is presented. A new incremental numerical formulation is presented to correctly handle the dependency of the AAR kinetics on the temperature field in case of cyclic temperature variation. A verification example is presented at the material level, along with qualitative assessment of the cracking pattern of an existing hydraulic structure affected by AAR. This last application at structural level demonstrates the efficiency of the suggested methodology and the feasibility within an industrial context.

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Numerical Model for Minimizing Risk of Damage in Repair System

Cited by 17 publications

References 5 publications

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Micromechanical Study of the Interface Properties in Concrete Repair Systems

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

Development of a computational multi-physical framework for the use of nonlinear explicit approach in the assessment of concrete structures affected by alkali-aggregate reaction

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